This photograph shows Skylab's Galactic X-Ray Mapping facility (S150), an astrophysics and space sciences investigation. An objective of this experiment was to extend the search for the origin of galactic x-rays beyond the sensitivity possible with short flights of small research rockets. This was accomplished by placing a large-area, soft x-ray detector in orbit to collect data for a much longer time. The S150 instrument was not in Skylab but in the instrument unit of the second stage of the Skylab-3 Saturn IB rocket.